There are basic "MLA" style logs available but they may not contain the detail level you require for Audit purposes;
The log contains a file report of access/change attempts. That is, Cisco Unified CallManager Administration generates a record of attempts to access or modify any directory or database component through Cisco Unified CallManager Administration. The change record includes the user name, date, time, window from which the change was made, and the success or failure status of the update.
The Trace File for MLA, Via RTMT (Trace Files) is where you will find the Logs;
Trace tab -> Trace & log central -> Collect files -> Cisco Role Based security
For more detailed logs you would need something like this product;
Cisco does offer some good Management/Monitoring products in the UC space. Have a look;
Key Features of Cisco Unified Operations Manager
Real-time visualization and monitoring of the entire Unified Communications system supports more efficient troubleshooting
Active service assurance ensures that devices and applications are functioning as they should, and reveals faults and performance issues before they affect service
Powerful diagnostic tests and troubleshooting capabilities rapidly isolate faults and increase productivity
Correlation, analysis, and presentation of voice service quality data and alerts make use of information available through Cisco Unified Service Monitor
Inventory and change monitoring enable tracking of complete details of unified communications devices and IP phone inventory
Cisco Unified Operations Manager does not deploy any agent software on the devices being monitored, so it will not disrupt system operations
Cisco Unified Operations Manager helps reduce system maintenance costs, improve productivity, and increase user satisfaction by providing a comprehensive monitoring, alerting, and troubleshooting view into the entire Cisco Unified Communications environment.
Hope this helps!
Im not here to plug any software, but I use Variphy to audit. It can take snapshots, then compare from other snapshots and spit out a report. Everything on the system from lines to users, everything.